Quantum Entanglement
(coming soon) Quantum Entanglement is a property of quantum systems that leads to much conflict with materialist ideas of local realism. Local realism suggests that a quantum particle exists in a particular state, even prior to measuring it, and that the reality of that state should be independent of any non-local influences. However, quantum entangled particles show that an observer who chooses to measure particles in different contexts will find that the particles will correlate in ways that seem impossible under local realism. This contextual nature of quantum statistics, shows that the reality of a quantum particle's state is not determined by local causality alone, but also by the context of the full experiment - including measurements which haven't been made yet. Background :"A simple classical analogy for 'entangled states' is Bertlmann's socks: :In that the axiom 'Bertlmann never wears matching socks' establishes a type of classically 'entangled' property of the 'two-sock system' which allows observers to make conclusions about each sock after observation of only one (in the same way that measuring the spin state of a single particle in a two-particle entangled state, tells the observer about the partner particle). :Entangled particles separated by vast (space-like) distances contain 'quantum mutual information' such that physical states that are completely undetermined prior to measurement will instantaneously 'collapse' into known states despite the impossibilty of a 'causal link' between them. :In the same way, if Bertlmann loses a sock before boarding a plane across the globe, a colleague who finds the missing sock can infer information about the colour of sock Bertlmann is still wearing despite being far too distant to observe him personally. ::The core difference is that the classical 'socks' have a fixed state regardless of measurement - specifically, it doesn't matter what properties you measure of the socks, the state (colour, size, length) is pre-determined. ::Whereas fully-entangled quantum particles have no pre-existing state as separate from the global state (e.g. a singlet state 'opposite spin' - but can be 'opposites' along any axis you choose to measure). ::The 'spooky action at a distance' Einstein refers to when confronted with quantum entanglement is that the state of the partner particle will align along the same axis the observer of the measured particle chose as the 'measurement basis' - implying either: 1. the particles had hidden 'rules' to determine which way to align under certain measurements (breaks Bell's theorem); 2. the particles were able to exert 'hidden forces' on one another at speeds greater than allowed in Einstein's Relativity (breaks locality); or 3. the final state of the particles can not be analysed in isolation to the measurement which determines that state (counter-factual indefiniteness)." Information Flow :"All information in quantum systems is, notwithstanding Bell’s theorem, localised. Measuring or otherwise interacting with a quantum system S has no effect on distant systems from which S is dynamically isolated, even if they are entangled with S. Using the Heisenberg picture to analyse quantum information processing makes this locality explicit, and reveals that under some circumstances (in particular, in Einstein-Podolski-Rosen experiments and in quantum teleportation) quantum information is transmitted through ‘classical’ (i.e. decoherent) information channels." Articles Entanglement is an inevitable feature of reality - Lisa Zyga, Phys.org, September 2017 (see also Richens2017 for the actual study) "Is entanglement really necessary for describing the physical world, or is it possible to have some post-quantum theory without entanglement? In a new study, physicists have mathematically proved that any theory that has a classical limit—meaning that it can describe our observations of the classical world by recovering classical theory under certain conditions—must contain entanglement. So despite the fact that entanglement goes against classical intuition, entanglement must be an inevitable feature of not only quantum theory but also any non-classical theory, even those that are yet to be developed." "Although the full proof is very detailed, the main idea behind it is simply that any theory that describes reality must behave like classical theory in some limit. This requirement seems pretty obvious, but as the physicists show, it imparts strong constraints on the structure of any non-classical theory. Quantum theory fulfills this requirement of having a classical limit through the process of decoherence. When a quantum system interacts with the outside environment, the system loses its quantum coherence and everything that makes it quantum. So the system becomes classical and behaves as expected by classical theory. Here, the physicists show that any non-classical theory that recovers classical theory must contain entangled states. To prove this, they assume the opposite: that such a theory does not have entanglement. Then they show that, without entanglement, any theory that recovers classical theory must be classical theory itself—a contradiction of the original hypothesis that the theory in question is non-classical. This result implies that the assumption that such a theory does not have entanglement is false, which means that any theory of this kind must have entanglement." ---- }} Category:Quantum Entanglement Category:Quantum Category:Quantum Philosophy